A mortar is an artillery piece having a relatively short smooth bore barrel which fires an explosive projectile in a high arched trajectory. The projectile is fin stabilized and a conventional projectile includes a relatively massive casing containing a propellant and an explosive charge which, upon detonation, causes fragmentation of the casing. In an improved design, the relatively massive casing is replaced by a light weight two-part configuration comprised of a composite structure surrounded by a shell of a light-weight metal such as aluminum.
The composite structure is a two phase structure having a filler of individual members, in the form of metal balls, contained in a matrix of thermoplastic. The composite structure has a longitudinal central cavity into which is placed an explosive charge. The arrangement provides for a greater lethality over the conventional projectile design.
The thin aluminum shell, however, is insufficient to withstand the acceleration forces when the projectile is launched and accordingly, the composite structure forms the structural element of the projectile. Since the metal balls are contained in a relatively weak thermoplastic matrix intended to fragment upon detonation, it is essential that the required amount of balls be placed in the matrix in a relatively homogeneous distribution. At the same time, areas where too many balls are packed tightly together might result in voids in other areas which can lead to structural failure causing the projectile to break apart after launch.
To date there has not been a relatively simple and accurate way to inspect the metal ball/thermoplastic composite structure prior to assembly. The present invention solves the problem.